Cylindrical mechanisms for controlling equipment are well-known. For example, U.S. Pat. No. 4,712,101, issued Dec. 8, 1987 and entitled "Control Mechanism For Electronic Apparatus," discloses a cylinder mounted on a rotatable shaft such that the shaft rotates with the cylinder. The cylinder also moves longitudinally relative to the shaft. A first encoder responsive to the rotation of the shaft adjusts a first electrical signal and a second encoder responsive to the linear movement of the cylinder relative to the shaft adjusts a second electrical signal. When applied to the mouse inputs of a computer, the cursor on the CRT display of the computer can be moved as a function of the rotation and the linear motion of the cylinder.
U.S. Pat. No. 4,724,715, issued Feb. 16, 1988 and entitled "Control Mechanism For Computer Keyboard And The Like," discloses a related mechanism for controlling equipment, such as a cursor on a CRT, wherein an analog element is rotatably mounted on a guide member and is movable relative to and longitudinally along the guide member. A first encoder senses rotation of the element relative to the guide member and a second encoder senses linear movement of the element relative to the guide member. In various embodiments of the above mechanisms, the user can also depress the entire mechanism to produce an additional signal capable of controlling a value or generating a signal usable for controlling a third parameter.
Other mechanisms employing a movable cylindrical element for providing control signals for use in controlling equipment are shown in, for example, U.S. Pat. Nos. 4,823,634, 4,896,554, and 4,982,618, all of which are inventions of Craig F. Culver. See also U.S. Pat. No. 4,799,049, issued January, 1989 to Avila.
However, a need arises for reducing the number of parts in these mechanisms, thereby decreasing assembly time and material cost, while maintaining a high degree of reliability. A need further arises for an improvement which may apply to all the controls described above.